I applied online. The process took 4 months. I interviewed at Transport UK London Bus (Stratford, London, England) in Nov 2015
Interview
1) Application - was pretty standard, a few competency questions at the end.
2) Online testing - Non Verbal Reasoning and Mechanical (SHL), I found the mechanical test easy and the non verbal was standard.
3) Video Interview - Logged in, was presented with the question, had 30 seconds to read it, and a minute to answer it. IIRC, there were about 12 questions, once the minute is up, it cuts to the next question regardless of whether you've answered the question in time or not, so be aware of that.
4) Interview - Lasted an hour, was competency questions for the first 15 mins and then the rest of it was technical.
Interview questions [1]
Question 1
1) Tell me about yourself?
2) How does an electrical train work?
3) Why are leaves on the track bad for the train?
4) How does an inverter work?